LTE (Long Term Evolution) systems (Non-Patent Literature 1) defined in 3GPP (3rd Generation Partnership Project) adopt OFDMA (Orthogonal Frequency Division Multiple Access) on downlinks. Thus, certain frequency and time radio resources are basically allocated to one mobile terminal apparatus (UE: User Equipment) through scheduling by a radio base station apparatus, and therefore users in the same cell are orthogonal to each other in frequency and time domains. However, since LTE systems are based on one-cell frequency reuse, a large amount of interference occurs from peripheral cells and the interference level at a UE located at cell edge is particularly high. Therefore, countermeasures for inter-cell interference are required to compensate for peripheral cell interference and maintain certain receiving quality.
3GPP is studying LTE-A (LTE-Advanced) systems to realize high-speed transmission with wider coverage than that of LTE systems. The LTE-A (LTE-Advanced) systems adopt coordinated multipoint transmission/reception (CoMP) as additional countermeasures for inter-cell interference. According to this CoMP, data and reference signals (RS) are simultaneously transmitted to mobile terminal apparatus 1 from radio base station apparatus 2A of the own cell (cell A) (Serving cell) and radio base station apparatus 2B of a peripheral cell (cell B) on downlinks as shown in FIG. 1. In this case, a control channel signal (PDCCH signal) is transmitted only from radio base station apparatus 2A of cell A, which is a serving cell.